OBJECTIVES: To determine the effects of ethacrynic acid, cysteine adduct, bumetanide and furosemide on endolymph ionic composition and endolymphatic dC potential in the cat and guinea pig. (The effects of bumetanide on endolymphatic dC potential in the cat has been reported but will be included to monitor viability of the preparation.) To determine effects of propranolol pretreatment on changes in N1, cochlear microphonics, endolymphatic dC potential and endolymph ionic composition produced by ethacrynic acid, cysteine adduct, furosemide and bumetanide. To determine effects of intracochlear administration of cyclic adenosine monophosphate on the diuretic-induced changes of cochlear parameters which are affected by propranolol. BIBLIOGRAPHIC REFERENCES: Brown, R.D. Manno, J.E., Daigneault, E.A. and Manno, B.R. "Effects of IV Bumetanide and Furosemide (Fur) on Cochlear Microphonics (CM) and N1 in the Beagle," Federation Proceedings 36, 571 (Abs.), 1977. Manno, J.E., Sterling, J., Brown, R.D., Daigneault, E.A. and Redetzki, H.M. "Microdetermination of Bumetanide and Furosemide by Reverse Phase High Pressure Liquid Chromatography," Federation Proceedings 36, 572 (Abs.), 1977.